1. Field of the Invention
This invention relates generally to fabrics for forming sleeves for receiving and protecting elongated items such as wiring harnesses and optical fiber cables, and more particularly to warp knitted self-curling fabrics therefor.
2. Background of the Invention
Protective sleeving is used throughout the automotive, marine and aerospace industries to organize and protect elongated items, such as wiring harnesses and optical fiber cables, for example. The sleeving surrounds the elongated items and protects them against cuts, abrasion, radiant heat, vibration induced wear and other harsh environmental threats. When positioned within protective sleeving, the wiring or cables are also held together in a neat bundle, allowing a multiplicity of different items to be handled as a sub-assembly, thus saving time and effort during integration of the items into its end environment.
Protective sleeving may be made by weaving or knitting filaments into a substrate and then resiliently biasing the substrate into a tubular form to define a central space for receiving the elongated items. Biasing may be effected by heating the filaments when the substrate is wrapped about a cylindrical mandrel, wherein the filaments take on a permanent set conforming to the shape of the mandrel. In addition, filaments can also be resiliently biased into a curved shape by applying chemicals thereto, as well as by cold working.
When substrates are biased into a tubular shape via the mechanisms described above, monofilaments are typically oriented in the “hoop” or circumferential direction of the tube. Monofilaments provide excellent stiffness and provide strong resilient biasing that maintains the substrate in the tubular shape. The biased monofilaments also tend to restore the substrate to its tubular shape in the absence of a distorting force, which is generally applied when the sleeve is manipulated to an open state to insert or remove an elongated item.
A significant disadvantage associated with sleeves that are biased into a tubular shape is that the biasing is effected by a separate step in the process of making the sleeve. The filaments comprising the substrate may be biased by cold working before manufacture of the sleeve or may be biased afterward by heating the substrate when wrapped about a mandrel, but these actions constitute an additional process that adds to the cost and the time required to produce the sleeve. Accordingly, it would be advantageous to be able to manufacture a tubular sleeve from a substrate that negates the need for secondary processes to impart the tubular shape on the substrate.